The necessary analytical procedures were developed in the first year of this grant, and during the second year research on the epoxide-diol pathway will be directed toward the isolation and/or synthesis of reactive metabolites of phenytoin, carbamazepine and pronethalol for evaluation of toxicity. The metabolites of interest include dihydrodiol, catechol, quinone and N-hydroxy derivatives of the three drugs. Ames tests will be used to test for cytotoxicity and mutagenicity. In vivo studies of the effects of acute and chronic administration of metabolites will be carried out in rats and mice (C57B1/6 and DBA/2). Samples of liver, kidney and adrenal tissue will be examined by light and electron microscopy for signs of toxicity. In addition, thymus tissue will be examined from animals treated with pronethalol. Urine samples (24 hr) will be collected from metabolite-treated animals and analyzed by HPLC and GC-MS-COM methods in order to study the metabolism of reactive intermediates. Proposed hydralazine studies are summarized in the San Antonio report. Work in computer science during 1979 will be directed towards the further enhancement of a PDP11-based system of programs for the interactive analysis of mass spectrometric data. Routines will be developed for obtaining quantitative results from selected ion detection data, together with estimates of probable error. Additional modes of three dimensional graphic presentation of data will be developed.